1. Field of the Invention
The present invention relates to a heat exchanger of the parallel flow type including a plurality of tubes extending in parallel with one another and stacked one on another and header tanks connected to laterally opposite ends of the tube stack. (See Diesel Kiki Col, Ltd. U.S. Pat. No. 5,036,914.)
2. Prior Art
The automotive parallel flow type heat exchanger generally comprises a plurality of tubes and fins stacked together one on another alternately, header tanks connected to laterally opposite ends of such a stack, and an inlet pipe connected to one header tank and an outlet pipe connected to the other header tank.
All the tubes constitute together a single passage between the headers so that heat exchanging medium (referred to hereinafter as refrigerant) may flow in parallel and in one pass (See Japanese Utility Model Application Disclosure Gazette No. 63(1988)-74970) or each header tank is provided therein with partitions to define a refrigerant passage folded plural times in zigzag fashion (See Japanese Patent Application Disclosure Gazette No. 63(1988)-34466).
However, such heat exchanges of the prior art inevitably enlarge the volume of each header tank since refrigerant flows through a single passage between the opposite headers whether this single passage is straight or in serpentine fashion. With such arrangement, the distribution of refrigerant from the header tank into the respective tubes smoothly occurs when the flow rate of refrigerant is relatively high, but the flow resistance within each header tank increases as the flow rate of refrigerant decreases down to medium or low levels and correspondingly the distributing efficiency as well as the heat exchanging efficiency is lowered.
Recently, the capacity-variable compressor has often been employed in a refrigerant cooling system and, accordingly, there is a serious need to achieve the maximum efficiency of the heat exchanger even during the low capacity operation.
Thus, a principal object of the present invention is to provide a heat exchanger with an improved heat exchanging efficiency in which the distribution of refrigerant to each tube is improved not only at high flow rates of refrigerant but also at medium or low flow rates of refrigerant. (For this object, see the U.S. Pat. No. 5,036,914, too.)